linux-kernel - Re: [PATCH] mm/vmalloc: Separate put pages and flush VM flags

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Message-ID: <21e2ed55-90f5-3e26-06ff-e4fd81709ffd@huawei.com>
Date:   Thu, 21 Jan 2021 10:44:20 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
CC:     <hch@....de>, <dja@...ens.net>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm/vmalloc: Separate put pages and flush VM flags

Hi:
On 2021/1/21 9:41, Rick Edgecombe wrote:
> When VM_MAP_PUT_PAGES was added, it was defined with the same value as
> VM_FLUSH_RESET_PERMS. This doesn't seem like it will cause any big

Good catch!

> functional problems other than some excess flushing for VM_MAP_PUT_PAGES
> allocations.
> 
> Redefine VM_MAP_PUT_PAGES to have its own value. Also, move the comment
> and remove whitespace for VM_KASAN such that the flags lower down are less
> likely to be missed in the future.
>> Fixes: b944afc9d64d ("mm: add a VM_MAP_PUT_PAGES flag for vmap")

Is this worth a Cc stable ?

> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> ---
>  include/linux/vmalloc.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> index 80c0181c411d..0b3dd135aa5d 100644
> --- a/include/linux/vmalloc.h
> +++ b/include/linux/vmalloc.h
> @@ -23,9 +23,6 @@ struct notifier_block;		/* in notifier.h */
>  #define VM_DMA_COHERENT		0x00000010	/* dma_alloc_coherent */
>  #define VM_UNINITIALIZED	0x00000020	/* vm_struct is not fully initialized */
>  #define VM_NO_GUARD		0x00000040      /* don't add guard page */
> -#define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
> -#define VM_MAP_PUT_PAGES	0x00000100	/* put pages and free array in vfree */
> -
>  /*
>   * VM_KASAN is used slighly differently depending on CONFIG_KASAN_VMALLOC.
>   *
> @@ -36,12 +33,13 @@ struct notifier_block;		/* in notifier.h */
>   * Otherwise, VM_KASAN is set for kasan_module_alloc() allocations and used to
>   * determine which allocations need the module shadow freed.
>   */
> -
> +#define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
>  /*
>   * Memory with VM_FLUSH_RESET_PERMS cannot be freed in an interrupt or with
>   * vfree_atomic().
>   */
>  #define VM_FLUSH_RESET_PERMS	0x00000100      /* Reset direct map and flush TLB on unmap */
> +#define VM_MAP_PUT_PAGES	0x00000200	/* put pages and free array in vfree */
>  
>  /* bits [20..32] reserved for arch specific ioremap internals */
>  
> 

Looks good to me.

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>